Current antiretroviral therapy is not curative and does not eradicate HIV-1 viremia. Rather, the virus persists and is merely suppressed during therapy. The source and dynamics of this persistent viremia is currently unknown. Determining the source of persistent viremia during combination antiretroviral therapy will inform future efforts aimed at viral eradication. To address these important issues the current study puts forward two hypotheses. First, to identify the source of persistent viremia in patients on suppressive therapy we must compare HIV populations in patient plasma to the HIV populations found in the cerebrospinal fluid (CSF), cells from peripheral blood and cells isolated from other tissues. Second, activating the latently HIV-infected cell will induce the expression of the integrated HIV genome making it vulnerable to immune-mediated killing and therapy. To test these hypotheses we seek to achieve three specific aims. First, we will characterize the HIV-1 genetic populations in plasma, CSF and a broad spectrum of HIV-infected cells from peripheral blood, gut associated lymphoid tissue (GALT), lymph node tissue (LNT), and bone marrow tissue (BMT) from patients on suppressive therapy using such methods as single-genome sequencing and single-proviral sequencing. The phylogenetic relatedness of the plasma-derived viral RNA sequences and intracellular viral DNA sequences will be determined. The comparison of HIV populations from plasma to different cellular and tissue compartments will allow us to investigate and seek to identify the source and genetic dynamics of persistent viremia in patients on suppressive therapy. For our second aim, we will apply peer-reviewed and published ligation-based molecular tools known as proximity ligation probes to specifically label and measure HIV virions and identify the cellular source of these particles. This will be important for identifying the cell lineage producing virions during suppressive therapy. Third, we will use new inhibitors of DNA methylation, protein methylation or histone deacetylation to stimulate cellular HIV transcription and therefore release of HIV from latently infected memory CD4+ T-cells, making the virus vulnerable to antiretroviral drugs. To accomplish this aim, we will culture CD4+ memory T-cells from patients on suppressive therapy and expose these cells to the new inhibitors. This research plan will bring together a diverse, multinational group of experts from Europe and United States specializing in HIV translational research, HIV clinical treatment, molecular genetics, and antiviral drug development.